In an attempt to obtain flame-retardant epoxy resins, a new diglycidylphosphine oxide, isobutylbis(glycidylpropylether)phosphine oxide (IHPO-Gly) was synthesized by reaction of isobutylbis(hydroxypropyl)phosphine oxide with epichlorohydrin and NaOH under phase transfer catalyst conditions. The thermal behaviour of IHPO-Gly was investigated by DSC and TGA and, together with thermal homopolymerization, isomerization and decomposition were detected. The reactivity of this novel diglycidyl compound was studied using boron trifluoride monoethylamine (BF(3)(.)MEA) or 4-dimethylaminopyridine (DMAP) as catalysts and 2,4-diaminotoluene (DAT), hexahydrophtalic acid anhydride (IPA) or dicyandiamide (DICY) as hardeners. The thermal and flame retardant properties of the final thermosets were studied and V-0 materials were obtained in all cases except when BF(3)(.)MEA was used as catalyst. (C) 2003 Elsevier Ltd. All rights reserved.